A MRAM (Magnetoresistive Random Access Memory) preferably includes a magnetoresistive element having a relatively large magnetoresistive change ratio (MR ratio). A magnetoresistive element having a large MR ratio includes a tunnel magnetoresistance element in which a tunnel barrier layer is made of magnesium oxide. Solid phase epitaxial growth may be employed to realize a good crystal structure in manufacturing the magnetoresistive element. Japanese Patent Application Publication No. 2010-166051 discloses a technique related to a magnetoresistance effect element (magnetoresistive element) or the like. In the magnetoresistance effect element disclosed in Japanese Patent Application Publication No. 2010-166051, a free layer has a composite structure in which a first ferromagnetic layer, an insertion layer and a second ferromagnetic layer are laminated in that order from the tunnel barrier layer side.
Along with the trend toward a high density of MRAM, as a volume of the magnetoresistive element is decreased, a thermal stability index is decreased and, thus, stability of a magnetization direction against thermal disturbance deteriorates. Japanese Patent Application Publication No. 2010-166051 discloses a method in which annealing is performed after formation of a laminated film including a tunnel barrier layer, a free layer and a cap layer in manufacturing a magnetoresistance effect element. However, it is difficult to realize magnetic characteristics (particularly, anisotropic magnetic field) enough to suppress a decrease in the thermal stability index in the annealing performed after the formation of the laminated film including the cap layer. Therefore, it is preferable to provide a method for manufacturing a magnetoresistive element which can improve magnetic characteristics such as an anisotropic magnetic field and the like.